The present invention relates generally to an improved wedge-lock fastener and associated installation and assembly methods and, in one advantageous embodiment, to a wedge-lock fastener designed such that the tongue of the wedge-lock fastener may be completely disposed within a counterbore defined by a workpiece engaged by the wedge-lock fastener.
Wedge-lock fasteners are utilized in a wide variety of applications. In a typical application, one or more wedge-lock fasteners are utilized to temporarily secure two or more workpieces together. While the workpieces are temporarily held together by the wedge-lock fasteners, permanent fasteners, such as rivets or the like, may be installed. Thereafter, the wedge-lock fasteners may be removed and reused.
By way of example, wedge-lock fasteners may be utilized during the assembly of an aircraft fuselage. In a traditional structure, stringers are temporarily affixed to the skin with a plurality of wedge-lock fasteners. The stringers are then riveted to the skin and the wedge-lock fasteners are removed from the skin/stringer assembly. Additionally, shear ties are temporarily secured to frames with a plurality of wedge-lock fasteners. After riveting the shear ties to the frames, these wedge-lock fasteners are also removed. The skin/stringer assembly is then temporarily fastened to the frame/shear tie assembly, such as by means of a plurality of wedge-lock fasteners. The skin/stringer assembly is then riveted to the frame/shear tie assembly, such as by riveting the shear ties to the skin. Thereafter, the wedge-lock fasteners may again be removed. Finally, stringer clips may be temporarily fastened to the frames and the stringers. After riveting the stringer clips to both the stringers and the frames, the wedge-lock fasteners may be removed. Thus, wedge-lock fasteners or other temporary fasteners may be repeatedly utilized during a number of the steps of the conventional process for assembling an aircraft fuselage.
While wedge-lock fasteners work well in a number of situations, a wedge-lock fastener is unsuitable for certain applications, as described below in conjunction with the conventional wedge-lock fastener 10 depicted in FIG. 1. As shown, a conventional wedge-lock fastener includes a shank 12 that extends lengthwise between a forward end 14 that is adapted to be placed in contact with one of the workpieces 16 to be clamped together, and an opposed rear end 18. The shank defines a central passage 20 opening through both the forward and rear ends. The wedge-lock fastener also includes a tong assembly extending lengthwise through the passage defined by the shank. The tong assembly includes a pair of tongs 22 extending through the opening defined by the forward end of the shank. In addition, the forward end of each tong includes a barb 24 extending laterally outward and defining a shoulder 26 for engaging a workpiece as described below. A tong assembly also includes a threaded portion 28 disposed rearward of the pair of tongs. The wedge-lock fastener also includes a tong nut 30 secured to the rear end of the shank and adapted to threadably engage the threaded portion of the tong assembly. Thus, the pair of tongs may be controllably advanced and withdrawn relative to the shank by the rotation of the tong nut relative to the shank.
A conventional wedge-lock fastener 10 also includes a grommet 32 that is sized to fit snugly within the passage 20 defined by the shank 12. The grommet 32 may be shrink-fitted, crimped, or may be an integral part of the tong assembly. In addition, the interior wall of the shank and the exterior surface of the grommet include lengthwise extending ribs and grooves that cooperate to guide the tong assembly in a lengthwise direction within the passage defined by the shank and to prevent rotation of the tong assembly relative to the shank. The grommet and associated grooves vary in shape and may be hexagonal or polygonal as well. The wedge-lock fastener also includes a tongue 34 disposed between the pair of tongs 22 and extending through the opening defined by the forward end 14 of the shank. The wedge-lock fastener typically includes a tongue retainer ring 36 disposed within the passage defined by the shank so as to effectively retain the rear end of the tongue within the shank and, in particular, between the forward end of the shank and the retainer ring.
During installation through the aligned holes defined by two or more workpieces 16, the tongs 22 are advanced relative to both the shank 12 and the tongue 34 by rotation of the tong nut 30 with respect to the shank. The tongs are extended such that the tongs extend beyond the tongue, thereby permitting the barbed forward ends 24 of the tongs to be collapsed or displaced toward and into contact with one another. The respective forward ends of the tongs and the tongue may then be inserted through the hole, which has a diameter slightly larger than the width of the barbed forward ends of the tongs once the barbed forward ends of the tongs have been collapsed or displaced toward and into contact with one another, but smaller than the width of the barbed forward ends of the tongs once the barbed forward ends of the tongs are separated by the tongue as described below.
In order to clamp a pair of workpieces 16 together, corresponding holes defined by the workpieces are aligned, and the respective forward ends of the tongs 22 and the tongue 34 are inserted through the aligned holes while the barbed forward ends 24 of the tongs are extended beyond the tongue and deflected toward one another. The tong nut 30 is then rotated in the opposite direction relative to the shank 12 so as to retract the tong assembly. The tong assembly is retracted until the workpieces are snugly engaged on one side by the forward end 14 of the shank and on the other side by the respective shoulders 26 defined by the barbed forward ends of the tongs. During the process of retracting the tongs, the barbed forward ends of the tongs draw alongside the tongue so as to spread the barbed forward ends of the tongs apart and into engagement with the workpiece, as shown in FIG. 1.
While a conventional wedge-lock fastener 10 provides for the secure engagement of two or more workpieces 16 as shown in FIG. 1, difficulties arise if one or more additional workpieces must be placed on or otherwise assembled with the workpieces that are clamped together by the wedge-lock fastener. As will be noted in FIG. 1, not only do the barbed forward ends 24 of the tongs 22 extend beyond the surface of the workpieces, but the tongue 34 can extend beyond the surface of the workpieces by a significant distance, depending upon the relative thickness of the workpieces. In order to accommodate the protrusion of the barbed forward ends of the tongs and the tongue beyond the surface of the workpieces, the additional workpiece that is to be placed thereupon may also define an opening through which the barbed forward ends of the tongs and the forward end of the tongue may extend. Especially for workpieces of a relatively large size, however, it may be difficult to place the additional workpiece upon the workpieces that are clamped together with the wedge-lock fasteners without scratching the additional workpiece with the protruding tongues of the wedge-lock fasteners.
By way of a more specific example, an alternative process for assembling aircraft fuselages is being developed. In this process, the stringers and frames are first temporarily fastened together with one or more wedge-lock fasteners or other temporary fasteners. In this regard, the frames define a number of mouse-holes in which the throat of the mouse-hole is smaller than the remainder or body of the mouse-hole. Generally T-shaped stringers are positioned relative to the frames so as to extend through respective mouse-holes defined by the frames. The relatively constricted throat of the mouse-holes is too narrow to simultaneously insert the stringers of a large skin/stringer assembly, thereby rendering the pre-assembly of the skin and the stringers impractical. Thus, the stringers are temporarily fastened to the frames by wedge-lock fasteners or the like that extend through assembly holes that define an appropriate frame of reference for the assembly. The skin is then to be assembled to the frame/stringer assembly while the stringers are temporarily fastened to the frames. However, the tongues of the conventional wedge-lock fasteners protrude, sometimes significantly, beyond the frame/stringer assembly, thereby preventing the straightforward placement of the skin upon the frame/stringer assembly and rendering the skin vulnerable to scratching by the protruding tongues of the wedge-lock fasteners. Thus, this alternative process for assembling aircraft fuselages cannot utilize conventional wedge-lock fasteners in a typical manner.
Since the stringers and the frames cannot be temporarily fastened with wedge-lock fasteners during this alternative assembly process, it is contemplated that the stringers for an entire panel could be placed upon the frames and the corresponding holes defined by the stringers and the frames could be aligned by hand, using gravity as a temporary restraint. As a result of the curvature of an aircraft fuselage, however, some stringers would have to be placed on the frames at a relatively great height, such as about 20 feet, with operators standing on stepladders, cherry pickers, or the like. The skin would then have to be placed carefully on the stringers and frames without disrupting their alignment and while simultaneously aligning corresponding holes in the skin with the aligned holes defined by the stringers and the frames. Once the frames, stringers and skins have been properly aligned, temporary fasteners, such as conventional wedge-lock fasteners, could be placed through these holes, and the assembly could then be rotated to ground level for the installation of permanent fasteners.
However, this alternative assembly technique suffers from a number of disadvantages, including the danger involved in assembling a very large, heavy structure while standing upon stepladders or cherry pickers during a portion of the process. In addition, the simultaneous alignment of the corresponding holes defined by the stringers, frames and skin is practically intractable. Finally, the reliance upon gravity as a temporary restraint may be insufficient to prevent motion of the stringers relative to the frames, which are typically disposed at an incline, particularly in the presence of vibration during the placement of the skin upon the frames and stringers.
Thus, it would be desirable to design an improved wedge-lock fastener capable of securely engaging a plurality of workpieces, while permitting an additional workpiece to be placed thereupon without making the additional workpiece susceptible of being scratched by the protruding tongue of the wedge-lock fastener. Additionally, it would be desirable to develop an improved method of assembling a plurality of workpieces with a wedge-lock fastener so as to permit an additional workpiece to be readily placed upon or otherwise positioned relative to a plurality of workpieces clamped together by a wedge-lock fastener.
An improved wedge-lock fastener and associated installation and assembly methods are therefore provided according to various aspects of the present invention. The wedge-lock fastener is designed to permit the distance by which the forward end of the tongue protrudes beyond the workpiece to be controlled. Correspondingly, a method for installing a wedge-lock fastener is provided in which the respective forward ends of the tongue and tongs are inserted through respective holes defined by two or more workpieces and the tongs are then retracted to clamp the workpieces together with the respective forward ends of the tongue and the tongs being disposed completely within a counterbore defined by a workpiece. Since the respective forward ends of the tongue and the tongs are completely disposed within a counterbore defined by one of the workpieces, a method for assembling a plurality of workpieces is also provided in which an additional workpiece is placed upon and attached to the workpieces that are secured by the wedge-lock fastener. For example, a skin can be placed upon an assembly of stringers and frames that are temporarily held together by a wedge-lock fastener without scratching the skin.
According to one aspect of the present invention, a wedge-lock fastener is provided that includes a shank defining a lengthwise extending passage opening through a forward end. The wedge-lock fastener also includes an adjustable spacer member adapted for controlled lengthwise movement relative to the shank. For example, the adjustable spacer may threadably engage the forward end of the shank. In this embodiment, for example, the forward end of the shank may be externally threaded with the adjustable spacer member being internally threaded and mounted upon the forward end of the shank in a surrounding relationship thereto. The forward end of the adjustable spacer member extends beyond the forward end of the shank by a selectable distance.
In the typical application, the wedge-lock fastener is adapted to clamp a plurality of workpieces. The adjustable spacer member is therefore preferably capable of extending beyond the forward end of the shank by a range of selectable distances that is at least as large as the anticipated variations in thickness of the plurality of workpieces. Thus, the wedge-lock fastener can securely clamp together a plurality of workpieces even as those workpieces vary somewhat in thickness.
In order to maintain the selectable distance, the wedge-lock fastener may include a locking member for securing the adjustable spacer member in position relative to the shank. The locking member may be, for example, a lock nut disposed upon and threadably engaging the shank rearward of the adjustable spacer member.
In order to effectively clamp the workpieces, the wedge-lock fastener also includes at least two tongs adapted for lengthwise movement relative to the shank and the adjustable spacer member. Each tong has a respective forward end extending beyond the forward ends of the shank and the adjustable spacer member. The wedge-lock fastener also includes a tongue disposed between the tongs. The tongue extends from a rear end within the passage defined by the shank to a forward end that extends beyond the forward ends of the shank and the adjustable spacer member.
In order to install the wedge-lock fastener, the tongue and the tongs of the wedge-lock fastener may be inserted through a hole defined by a workpiece and, more commonly, by a pair of aligned holes defined by first and second workpieces. For example, a plurality of stringers may be positioned relative to a plurality of frames such that respective holes defined by the stringers and frames are aligned and the respective forward ends of the tongue and at least two tongs of the wedge-lock fastener may be inserted therethrough. The position of the tongue relative to the workpiece is then altered by controllably moving the adjustable spacer member relative to the shank of the wedge-lock fastener, such as by threadably advancing or retracting the adjustable spacer member relative to the shank. The movement of the adjustable spacer member relative to the shank of the wedge-lock fastener correspondingly adjusts the distance by which the adjustable spacer member extends beyond the shank and, in turn, similarly adjusts the position of the tongue relative to the workpiece. For example, as the adjustable spacer member is advanced so as to extend further beyond the shank, the tongue is correspondingly retracted toward the workpiece. Alternatively, as the adjustable spacer member is retracted so as not to extend as far beyond the shank, the tongue is correspondingly extended further beyond the workpiece. Once the tongue is properly positioned relative to the workpiece(s), the adjustable spacer member may be secured in position relative to the shank. Thereafter, the tongs are retracted relative to the tongue such that the respective forward ends of the tongs are urged outwardly by the tongue and operatively engage the workpiece.
In instances in which the wedge-lock fastener serves to clamp two or more workpieces together, one of the workpieces may define a counterbore into which the aligned holes defined by the workpieces open. In this embodiment, the wedge-lock fastener is inserted from the side of the workpieces opposite the counterbore. According to this aspect of the present invention, the forward ends of the tongue and the tongs may be positioned completely within the counterbore. In this regard, the adjustable spacer member may be controllably moved relative to the shank until the forward end of the tongue is within the counterbore. After retracting the tongs so as to operatively engage the workpieces, another workpiece, such as the skin of an aircraft or other structure, may be placed on the surface of the workpieces through which the counterbore opens while the wedge-lock fastener remains installed. Since the respective forward ends of the tongue and the tongs are completely disposed within the counterbore, however, the additional workpiece is not scratched and may be readily positioned upon the other workpieces that remain temporarily fastened together.
In instances in which the forward end of the tongue still extends beyond the surface of the workpieces once the tongs have been retracted so as to engage the workpieces, at least the forward end of the tongue that extends beyond the surface of the workpieces may be removed. For example, that portion of the tongue that extends beyond the surface of the workpieces may either be cut off or ground off. An additional workpiece may then be placed upon the other workpieces that remain fastened together by the wedge-lock fastener without scratching the additional workpiece. Moreover, even after the forward end of the tongue has been removed, the wedge-lock fastener may accommodate variations in the thickness of the workpieces that are clamped or temporarily fastened together by controllably moving the adjustable spacer member relative to the shank. In this regard, the wedge-lock fastener is adapted to securely clamp workpieces together that vary in thickness by any amount within the range of controlled movement of the adjustable spacer member relative to the shank of the wedge-lock fastener.
The wedge-lock fastener of the present invention is therefore adapted to securely clamp a plurality of workpieces together. By permitting the position of the tongue relative to the workpieces to be controlled by lengthwise movement of an adjustable spacer member relative to the shank, the wedge-lock fastener can be mounted such that the respective forward ends of the tongue and the tongs are disposed within a counterbore defined by one of the workpieces. Moreover, an installation method of the present invention provides for the removal of at least a forward end of the tongue if the forward end of the tongue otherwise extends beyond the surface of the workpiece. As such, an additional workpiece can be placed upon the plurality of workpieces that are temporarily clamped together by the wedge-lock fastener without scratching the additional workpiece or otherwise impairing the assembly process. In one exemplary application, the wedge-lock fastener may temporarily fasten the stringers and frames together while a skin is mounted thereto. After permanently fastening the skin to the stringers and frames, the wedge-lock fasteners may be removed, thereby simplifying the process of assembling an aircraft fuselage or other structure.